Data Structure Binary Tree: Inorder Tree Traversal without Recursion

http://www.geeksforgeeks.org/inorder-tree-traversal-without-recursion/

 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <queue>
 5 #include <stack>
 6 using namespace std;
 7 
 8 struct node {
 9     int data;
10     struct node *left, *right;
11     node() : data(0), left(NULL), right(NULL) { }
12     node(int d) : data(d), left(NULL), right(NULL) { }
13 };
14 
15 void print(node *root) {
16     stack<node*> S;
17     if (!root) return;
18     node *cur = root;
19     while (1) {
20         if (cur) {
21             S.push(cur);
22             cur = cur->left;
23         }
24         else if (!S.empty()) {
25             cur = S.top();
26             S.pop();
27             cout << cur->data << " ";
28             cur = cur->right;
29         }
30         else break;
31     }
32 }
33 
34 
35 int main() {
36     struct node* root = new node(1);
37     root->left = new node(2);
38     root->right = new node(3);
39     root->left->left = new node(4);
40     root->left->right = new node(5);
41     print(root);
42     return 0;
43 }